J Synchrotron Radiat
November 2023
The Femtosecond X-ray Experiments (FXE) instrument at the European X-ray Free-Electron Laser (EuXFEL) provides an optimized platform for investigations of ultrafast physical, chemical and biological processes. It operates in the energy range 4.7-20 keV accommodating flexible and versatile environments for a wide range of samples using diverse ultrafast X-ray spectroscopic, scattering and diffraction techniques.
View Article and Find Full Text PDFThe high pulse intensity and repetition rate of the European X-ray Free-Electron Laser (EuXFEL) provide superior temporal resolution compared with other X-ray sources. In combination with MHz X-ray microscopy techniques, it offers a unique opportunity to achieve superior contrast and spatial resolution in applications demanding high temporal resolution. In both live visualization and offline data analysis for microscopy experiments, baseline normalization is essential for further processing steps such as phase retrieval and modal decomposition.
View Article and Find Full Text PDFNew synthetic hybrid materials and their increasing complexity have placed growing demands on crystal growth for single-crystal X-ray diffraction analysis. Unfortunately, not all chemical systems are conducive to the isolation of single crystals for traditional characterization. Here, small-molecule serial femtosecond crystallography (smSFX) at atomic resolution (0.
View Article and Find Full Text PDFSerial femtosecond crystallography is a rapidly developing method for determining the structure of biomolecules for samples which have proven challenging with conventional X-ray crystallography, such as for membrane proteins and microcrystals, or for time-resolved studies. The European XFEL, the first high repetition rate hard X-ray free electron laser, provides the ability to record diffraction data at more than an order of magnitude faster than previously achievable, putting increased demand on sample delivery and data processing. This work describes a publicly available serial femtosecond crystallography dataset collected at the SPB/SFX instrument at the European XFEL.
View Article and Find Full Text PDFThe European X-ray Free-Electron Laser Facility in Germany delivers x-ray pulses with femtosecond pulse duration at a repetition rate of up to 4.5 MHz. The free-electron laser radiation is created by the self-amplified spontaneous emission (SASE) process, whose stochastic nature gives rise to shot-to-shot fluctuations in most beam properties, including spectrum, pulse energy, spatial profile, wavefront, and temporal profile.
View Article and Find Full Text PDFThe specific interaction of allergens with IgE antibodies and the allergen mediated cross-linking of receptor-bound IgE are key events of allergic diseases. The elucidation of the IgE binding sites (the epitopes) on the allergen surface is an important goal of allergy research. Only few allergen-specific IgE epitopes have been determined experimentally to date.
View Article and Find Full Text PDFHigh-quality high-multiplicity X-ray diffraction data were collected on five different crystals of thaumatin using a homogeneous-profile X-ray beam at E = 8 keV to investigate the counteracting effects of increased multiplicity and increased radiation damage on the quality of anomalous diffraction data collected on macromolecular crystals. By comparing sulfur substructures obtained from subsets of the data selected as a function of absorbed X-ray dose with sulfur positions in the respective refined reference structures, the doses at which the highest quality of anomalous differences could be obtained were identified for the five crystals. A statistic σ{ΔF}, calculated as the width σ of the normalized distribution of a set {ΔF} of anomalous differences collected at a dose D, is suggested as a measure of anomalous data quality as a function of dose.
View Article and Find Full Text PDFBackground: Group 2 and 3 grass pollen allergens are major allergens with high allergenic activity and exhibit structural similarity with the C-terminal portion of major group 1 allergens. In this study, we aimed to determine the crystal structure of timothy grass pollen allergen, Phl p 3, and to study its IgE recognition and cross-reactivity with group 2 and group 1 allergens.
Methods: The three-dimensional structure of Phl p 3 was solved by X-ray crystallography and compared with the structures of group 1 and 2 grass pollen allergens.
The structure determination of major allergens is a prerequisite for analyzing surface exposed areas of the allergen and for mapping conformational epitopes. These may be determined by experimental methods including crystallographic and NMR-based approaches or predicted by computational methods. In this review we summarize the existing structural information on allergens and their classification in protein fold families.
View Article and Find Full Text PDFThe major turnip (Brassica rapa) pollen allergen, belongs to a family of calcium-binding proteins (i.e., two EF-hand proteins), which occur as highly cross-reactive allergens in pollen of weeds, grasses and trees.
View Article and Find Full Text PDFBackground: More than 90% of house dust mite-allergic patients are sensitized to the major Dermatophagoides pteronyssinus allergen, Der p 2. The aim of this study was to develop and characterize an allergy vaccine based on carrier-bound Der p 2 peptides, which should allow reducing IgE- and T-cell-mediated side-effects during specific immunotherapy (SIT).
Methods: Five Der p 2 peptides (P1-P5) were synthesized and analyzed regarding IgE reactivity and allergenic activity.
Background: The experimental determination of conformational allergen epitopes recognized by IgE is a difficult task because they often involve discontinuous amino acid residues, being separated in the primary allergen sequence, and require the correct allergen fold.
Objective: We sought to develop a computational tool for the localization of conformational IgE epitopes by using a structure-based comparison of allergen surfaces and IgE cross-reactivity data.
Methods: Our approach involves the quantitative analysis of geometric and physicochemical surface parameters and the subsequent correlation of surface similarity scores to immunologic data.
The synthesis of N-heterocyclic carbene adducts of alkynyl lithium and magnesium is achieved, and different degrees of association are observed. Reaction of strontium amide nacnacSrN(SiMe(3))(2)(thf) (nacnac = CH(CMe2,6-iPr(2)C(6)H(3)N)(2)) with PhC[triple bond]CH in THF yields the dimeric alkynyl complex [nacnacSr(thf)(mu-C[triple bond]CPh)](2) which shows an interesting coordination geometry around the metal center. The compound retains the THF molecules, unlike its lighter congener, even in hydrocarbon solvents.
View Article and Find Full Text PDFSubstitution reactions of rhenium(V) oxo precursors [ReOCl3(PPh3)2] or [NBu4][ReOCl4] with the bidentate acetylacetone-derived ketoamine ligands APOH = 4-anilino-3-penten-2-one, DPOH = 4-[2,6-dimethylanilino]-3-penten-2-one, and MTPOH = 4-[2-(methylthio)anilino]-3-penten-2-one gave the complexes [ReO(APO)Cl2(PPh3)] (1), [ReO(DPO)Cl2(PPh3)] (2), and [NBu4][ReOLCl3] (3, L = APO; 4, L = DPO; 5, L = MTPO), respectively. All complexes exhibit only one ketoamino chelate, independent of the amount of ligand added to the rhenium precursors. The complexes were characterized by 1H and 13C NMR spectroscopy.
View Article and Find Full Text PDFThere are only a few case reports regarding the anaesthetic management of a patient with Huntington's chorea and the best anaesthetic technique is yet to be established for those patients which are at higher risk of perioperative complications. We describe the successful management of a 30-year-old patient suffering from Huntington's chorea admitted for urgent appendectomy. To minimize the risk of aspiration, the trachea was intubated using a fiberscope with the patient sedated and spontaneously breathing.
View Article and Find Full Text PDFActa Crystallogr D Biol Crystallogr
November 2003
Using the signal of naturally inbuilt or artificially introduced anomalous scatterers to derive initial phases in a macromolecular crystal structure determination has become routine in recent years. In the context of high-throughput crystallography in particular, MAD and SAD (multiple- and single-wavelength anomalous dispersion) methods are central tools. For both techniques, a crucial step is the determination of the substructure of anomalous scatterers; subsequent phasing procedures will profit from a substructure model that is as accurate as possible.
View Article and Find Full Text PDFMolybdenum dioxo compounds [MoO2Cl(eta 2-pz)] and [MoO2(eta 2-pz)2] with pz = eta (2)-3,5-di-tert-butylpyrazolate have been synthesized; crystallographic data, catalytic activity, and oxo transfer properties are described.
View Article and Find Full Text PDFJ Antibiot (Tokyo)
September 2001
Two novel secondary metabolites, bagremycin A (2) and B (3), were detected in the culture filtrate of Streptomyces sp. Tü 4128 by HPLC-diode-array screening. They are phenol esters of 3-amino-4-hydroxybenzoic acid with a derivative of p-coumaric acid and show a moderate activity against gram-positive bacteria and some fungi.
View Article and Find Full Text PDFFrom 1980 to 1987, 243 evaluable patients with pT1, pT2 (less than 3 centimeters in diameter), N0, M0, invasive breast cancer were treated with "quadrantectomy" with axillary dissection followed by electron beam radiation therapy (QUART) at the St. Bortolo Hospital, Vicenza. Stage II patients received adjuvant chemotherapy (CMF) if preperimenopausal or hormonotherapy (tamoxifen) if postmenopausal.
View Article and Find Full Text PDFThe main anesthesiological problem in TEAC operations is the possibility of evaluating the degree of tolerance after carotid artery clamping. When facing this situation, some anesthesiologists prefer to administer general anesthesia, others prefer loco-regional anesthesia. On the basis of their background and experience, the Authors, from 1.
View Article and Find Full Text PDFThe thrombogenicity of the graft materials is a significant factor incriminated in early failures. Some improvements have been achieved by modification of physical characteristics of the material as porosity, compliance, durability in order to improve patency rates. Platelets are major determinants of thrombus formation and may still be thrombogenic by activation of the coagulation enzymes.
View Article and Find Full Text PDFThe work has the purpose to draw some prognostic indications and therapeutical directions in the aorto-iliac arteriosclerotic disease, with reference to the preoperative arteriographic and morphoscillographic reports. In the 94 patients, corresponding to 140 limbs operated on, it was possible to remark the progression in worsening of the sphygmic activity in the limbs segments goes along with a deterioration of the surgical results, and the prognosis is particularly severe when the minimum values of total vascular caliber are remarked at thighs.
View Article and Find Full Text PDFMinerva Cardioangiol
December 1983